1. Field of the Invention.
The present invention is directed to a fluid blocking device for a pipeline to form a fluid tight seal between an opening in the wall of the pipeline and a saddle fitting over the opening of the pipeline wall.
2. Prior Art.
Fluid blocking or stopping devices are well known in the pipeline industry. In one type of fluid blocking device, a saddle fitting fits over an opening in the wall of the pipeline. A resilient and deformable elongated plug or blocking plate is movable perpendicular to the axis of the pipeline and through the opening in the pipeline. One type of plug or blocking plate is a flat, flexible, usually elastomer paddle, sealing element or stopper. When moved into place within the pipeline, the plug deforms to the contours of the interior of the pipeline and blocks passage of fluid through the pipeline. The plug is, thus, in fluid tight engagement with the inside! wall of the pipeline. It is critical that a fluid tight seal is maintained not only in the pipeline itself but between the saddle fitting and the opening in the pipe. Any deviations can allow fluid to flow.
The resilient plug or blocking plate is forced through the fitting and into the pipeline annulus, by activation of a line stopping device compressed against the pipeline annulus and the fitting until the blocking plate is sealed perpendicular to the pipeline axis.
The saddle fitting is specially designed to allow entry and passage of the blocking plate into the corresponding pipeline. The fitting is attached to the pipeline and tapped through to provide an access hole into the pipeline. When attaching the steel, iron, or plastic fitting, it usually is not possible to weld, fuse, or attach the fitting to the pipeline so that there is a smooth transition surface from the diametrical bore of the fitting to the outside pipeline surface.
The transitional surface may contain voids that increase that portion of the bore between the fitting and the pipeline, or include excessive joining materials that protrude and reduce that transition surface diametrical bore to less than the fitting bore. Additionally, the hole tapped into the pipeline is usually a diameter that is smaller than the fitting bore, providing an irregular transition surface.
There is a need, therefore, for a fluid blocking device that will adequately and totally seal to block the flow of fluid through the pipeline and, at the same time, to prevent fluid flow or leakage between the fitting and the opening in the pipeline wall.